A hero from previous games:
Seeing Gold or Silver, would actaully be great to see, they could show us how they've changed during the games, maybe they changed their look, or changed their apprearance, but it would be great to see this actually happen in the coming X/Y Games.

There's actually a lot of potential with bringing Silver in for a cameo beyond witnessing his new maturity since GSC/HGSS. He could not only tell us about his long time rival (us, obviously), but also about Team Rocket and whatever really happened to his father, Giovanni, after that scene in the cave from the Celebi event.